Devices for the treatment of waste water are known and one such device is disclosed in U.S. Pat. No. 5,874,740.
Microbiologically contaminated liquids (such as for example wastewater from sewage plants) may be disinfected in a particularly environmentally protective manner by irradiating them with ultraviolet radiation. For this purpose, various irradiation devices are known in the prior art. In numerous cases, the problem arises that the lamp units of the radiation devices become externally contaminated. In particular, in the case of waters having a high alkaline earth ion content, precipitation of hardness constituents takes place to form encrustations which firmly adhere to the encasing tube surfaces and which are virtually unpreventable or removable by mechanical means.
In the abovementioned patent, a device is proposed in which annular chambers surround the lamp units. The chambers are situated at the surface of the encasing tubes and are sealed there by two O-rings. The interior of the chambers is filled with a cleaning liquid (for example phosphoric acid) via a supply device. To clean the surface of the lamp unit, the chamber filled with cleaning liquid is moved to and fro on the surface, as a result of which loosely adhering contaminants are pushed aside whereas firmly adhering encrustations are dissolved by means of the cleaning liquid.
In practice, this device functions only to a limited extent since the O-ring seals of the chamber in contact with the encasing tube surface react very sensitively to mechanical damage or dimensional deviations and in addition, the chemical action of the cleaning liquid on the encasing tube surface is inadequate without mechanical aid to prevent the formation of encrustations or to remove them. The exposure times are too short for this purpose.
Accordingly, it is Applicant's intent to provide a UV-Irradiation device that is capable (even at high contents of alkaline earths is the wastewater to treated) to counteract and to prevent effectively, the formation of encrustations on the encasing tube surface.